The present study aims to analyze the mechanical and histopathological aspects of flexor tendon healing focusing on the suture placement site in a vascular or in an avascular region. A total of 83 rabbits were submitted to a Kessler-type central suture in the vascularized tendon region TN group and in the avascular tendon region FC group.
The operated limb was immobilized for 3 weeks. The animals were sacrificed in the immediate postoperative period, and at 2, 3 and 6 weeks after the procedure. The mechanical properties studied were: maximumload, stress at maximumload,modulus of elasticity, energy at maximum load, and energy per area. The contralateral tendon was used as control.
The histopathological study was descriptive. The analysis of the mechanical properties showed similar behavior in both groups, with stabilization or discrete increased values between the immediate period and 3 weeks after the procedure, and marked increased values at 6 weeks.
Histopathology demonstrated that the healing process was similar in the TN and FC groups. Central suture placement in the vascularized or avascular fibrocartilaginous region results in no differences in the biomechanical and histopathological aspects of flexor tendon healing in rabbits.
O membro operado foi imobilizado por 3 semanas. In the treatment of zone II flexor tendon injuries, central suture placement in the tendon palmar region to limit vascular injury is a classic approach. Primary and secondary repairs of flexor and extensor tendon injuries. In: Jupiter JB, editor. Flynn's hand surgery. Primary care of flexor tendon injuries.
Rehabilitation of the hand: surgery and therapy. Louis: Mosby; However, experimental studies have concluded that the dorsal positioning of the central suture results in greater resistance compared to palmar suturing. Work of flexion after flexor tendon repair according to the placement of sutures. Comparative mechanical analysis of dorsal versus palmar placement of core suture for flexor tendon repairs.
Tensile strength of flexor tendon repairs in a dynamic cadaver model. A randomized biomechanical study of zone II human flexor tendon repairs analyzed in a linear model. Dorsal-enhanced sutures improve tension resistance of tendon repair.
J Hand Surg [Br] ;27 02 : The controversy between placing the central suture in the dorsal tendon region and obtaining greater resistance, but possibly impairing blood supply to the tendon, or placing the suture in the palmar region to preserve irrigation, but achieving less resistance, persists at the surgical practice. Biologic aspects of flexor tendon laceration and repair.
The present study aimed to analyze the mechanical and histopathological aspects of flexor tendon healing focusing on suture placement at the vascular or avascular region.
The study design was previously approved by the Ethics Committee on Animal Experimentation of the institution. The animals were divided into groups according to the location of the suture: normal tendon group TN sutured at the vascularized region; and fibrocartilage group FC , sutured at the avascular region.
Each group was subdivided into four subgroups according to the postoperative follow-up time, which were immediate, and of 2, 3, and 6 weeks Tables 1 and 2. The deep digital flexor tendon was used. This tendon is located in the ankle region, within the osteofibrous channel, and it is surrounded by synovial tissue, where it presents an elliptical nodule, in which the region presenting epithelium and blood vessels is referred to as normal tendon in this investigation, whereas the whitish, avascular region is referred to as fibrocartilaginous tendon.
The influence of mechanical forces on the glycosaminoglycan content of the rabbit flexor digitorum profundus tendon. Fibrous vs. Fibrocartilaginous Enthesis. Fibrous Enthesis Indirect Attachment. Fibrocartilaginous Enthesis Direct Attachment. Metaphysis and diaphysis of long bones. Epiphysis and apophysis. Perforating mineralized collagen fibers.
Angle of Insertion. Insertion angle changes slightly during motion. Insertion angle changes greatly during motion thus prone to overuse injury. Deltoid-humerus attachment, adductor magnus-linea aspera attachment, pronator teres attachment.
The deliberate, slow lowering towards the ground is eccentric exercise for the Achilles tendon Excessive tension on tendons while they are healing can cause increased pain, slowed healing, or sometimes even further injury.
Physical therapists design tendon treatment programs with activities that provide gradual increases in tendon stress, so that the body can progressively adapt to high-intensity tendon activities such as those required in sports or heavy work.
Bone Healing Considerations Bones heal best when loads are applied to them. Weight bearing activities through injured bones stimulates an increase in bone growth at injury sites and a subsequent increase in bone strength. This concept is why immobilizer boots are often used in ankle and foot fractures rather than plaster casts. Allowing patients to walk while protecting their healing bone allows the bony repair process to occur faster and more thoroughly than keeping weight entirely off of a fracture site.
After a fracture, even if a patient is allowed to bear weight, the injured bone should be immobilized so that the healing process can occur. Allowing too much movement at a fracture site too early in the healing process can lead to delays in fracture repair. Initial rehabilitation after a bone fracture often focuses on normalizing body movement in regions around the fracture site. Promoting general circulation through aerobic activity and strength training in other body parts can help with the bone healing process.
As a fracture knits and becomes sufficiently stable, rehabilitation activity is focused more on the body part that has been fractured. Ligament Healing Considerations Ligaments attach bones to other bones. They generally have a more limited blood supply than either muscle or tendon — lengthening their healing time.
Ankle sprains and ligamentous tears in the knee such as an Anterior Cruciate Ligament injury are two common ligament injuries. There are 3 grades of ligament sprain.
Cartilage Healing Considerations Cartilage is avascular, meaning that it has no blood supply. The lack of blood circulation in cartilage means that it is a very slow-healing type of tissue.
Nutrition to cartilage is maintained by fluid in the joints, which lubricates the tissue. However, the role of lymphatic vessels in tendon disease has been neglected so far. To our knowledge there is no literature available on the lymphatic drainage in common tendon disorders such as tendinopathy, calcific tendinitis, or chronic tendon inflammation due to mechanic overuse. Recently, we have shown that intact rat Achilles tendons are void of lymphatics, which start to grow into the tendon repair tissue upon injury Tempfer et al.
Whether lymphatic ingrowth is a cause for impaired tissue quality and scar formation or merely a side effect requires further investigation. This may pave the way for future attempts to target lymphatic vessels to improve tendon regeneration, as it is successfully performed in other, non-musculoskeletal diseases, such as corneal and ocular surface inflammation Bock et al.
These cells display mesenchymal stem cell MSC —like properties, displaying plastic adherence and a differentiation potential toward the osteoblast, adipocyte, and chondrocyte lineage.
We have shown that perivascular cells of the human supraspinatus tendon harbor a population of cells expressing both tendon- and stem cell associated markers Tempfer et al. This is well in line with the finding that perivascular cells derived from a variety of tissues, such as skeletal muscle, pancreas, adipose tissue, and placenta show MSC—properties Crisan et al. Interestingly, Mienaltowski et al. Both cell sources were negative for the perivascular surface marker CD and a differential expression pattern for the vascular marker endomucin as well as for tenomodulin and scleraxis.
Generally, the role of perivascular MSCs in regeneration remains a matter of debate. Caplan A. In diseases such as calcific tendinitis or in the formation of bony enthesophytes in spondyloarthritis, ectopic bone is formed within tendons. Recently, Lee CH et al. However, in order to fully harness the regenerative capacity of tendon stem cells we need to gain further insight into the in vivo identity of these cells and how they are modulated by the local niche.
So far, this remains experimentally challenging due to the lack of tendon-specific markers. Peritendinous adhesions often lead to significant functional impairment after tendon surgery. In a rabbit study, three main factors have been identified, which in combination support the formation of adhesions: i suture of the partially damaged tendon, ii excision of the synovial sheath, and iii immobilization.
If only one of these factors is avoided, adhesion formation can be significantly reduced Matthews and Richards, As nutrition of sheathed tendons is mainly provided by diffusion from the synovial membrane, the local loss of this tissue combined with a fibrin clot on the avascular outer layer of the tendon causes invasion of microvessels resulting in the formation of fibrous adhesions Pennington, More recently, tendon adhesion formation using a mouse model for flexor tendon injury has been demonstrated to follow a typical wound healing response, with overlapping phases of inflammation, vessel ingrowth, and an increase in apoptotic cells over a follow-up time-period of days Wong et al.
Current research-based strategies include the use of multilayer membranes loaded with non-steroidal anti-inflammatory drugs NSAIDs to prevent fibrosis, mimicking the synovial membrane Jiang et al. As Achilles tendinopathy AT is the most frequent and best studied form of this disease, we will focus on this particular tendon.
AT often affects people with high levels of sports activities. AT is characterized by pain in the tendon during initial loading, subsiding with continued activity; as the condition becomes chronic, pain can be persistent. Overuse is considered to be the underlying cause; however the etiology and pathogenesis have not yet been fully clarified. Similarly, the source of the pain and the underlying mechanisms of pain remain unclear.
Histologically, matrix disruption is commonly observed in AT, but is not necessarily involved in the pathogenesis as it also occurs in asymptomatic tendons Magnan et al. Neovascularization is commonly seen in AT, as shown by Doppler sonography Ohberg et al.
As mentioned above, during tendon development, high levels of VEGF are expressed. Molecules that are developmentally regulated are often re-expressed during the disease state. Indeed, the expression of VEGF in degenerative and spontaneously ruptured Achilles tendons is detectable at high concentrations when compared with adult, healthy Achilles tendons Pufe et al. In vitro , cyclic mechanical load induces the expression of VEGF and hypoxia inducible factor 1 HIF-1 in a frequency dependent fashion, indicating this mechanism being involved in tendon cell response to overload Petersen et al.
Some authors report AT to be a result of an inadequate repair process following microtrauma, i. Because of the lack of blood vessels within the mid portion of the tendon a neurogenic inflammatory process is activated to repair these microruptures. This neurogenic inflammation occurs in the tissue surrounding the Achilles tendon and matrix and induces the expression of metalloproteinases MMPs responsible for the degradation of extracellular matrix.
VEGF not only promotes angiogenesis, but also upregulates the expression of MMPs and downregulates tissue inhibitors of metalloproteinases TIMP-3 , further progressing the remodeling of the tendon tissue van Sterkenburg and van Dijk, They proliferate less and have a greater potential do undergo osteogenic and chondrogenic differentiation Rui et al.
Indeed, mineralization processes are also found in human AT and patella tendinopathy. One study on human tendinopathic tissue demonstrated that some mineralized deposits in Achilles and patella tendons are formed by a process resembling endochondral ossification, with bone formation and remodeling mediated by populations of osteoblasts and osteoclasts Fenwick et al.
Regarding treatment strategies for AT, eccentric loading e. Interestingly, this method also reduces the number of neovessels in the affected area, which is considered to be causative for the beneficial outcome Ohberg and Alfredson, Similarly, a combination of cryotherapy and compression of the tendinopathic area was shown to be an effective treatment, leading to a significant reduction of tendon blood flow Knobloch et al.
Also the use of topical nitroglycerin and low level laser irradiation are discussed to exert their positive effects by affecting tendon microcirculation. However, for both therapies the underlying mechanisms of action remain poorly understood Knobloch, Another area often affected is the adult enthesis organ that connects tendons with bone, allowing the transmission of force from muscle to bone.
The Achilles enthesis is frequently affected by non-inflammatory enthesopathies due to overuse or microtraumas and inflammation may occur resulting in major pain and disability. However, the underlying intrinsic and extrinsic factors also remain poorly understood. Generally, mineralized and non-mineralized entheses can be differentiated. The Achilles tendon enthesis organ is mineralized and four zones can be distinguished: Zone 1 is built of dense fibrous connective tissue the tendon proper , and the extracellular matrix ECM is mainly composed of collagen type I and III.
Zone 2 consists of non-mineralized fibrocartilage and fibrochondrocytes. Zone 3 is formed of mineralized fibrocartilage with fibrochondrocytes, the predominant collagen being Col II next to I and X as well as calcium phosphate crystals. Between Zone 2 and Zone 3 the so called tidemark forms the boundary between soft, non-mineralized, and hard, mineralized tissue. Zone 4 finally is made up of the bone itself Benjamin and McGonagle, ; Apostolakos et al.
This gradual transition from compliant soft tissue to rigid bone absorbs local stress concentrations minimizing the risk of injury. Further, it has been reported that there is no direct cellular communication between bone and tendon tissue and the fibrocartilage at the enthesis acts as a barrier between cells in the two tissues Ralphs et al.
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